Edward
There is no "common practice" for BGA's.  It depends on the PWB shop and
customer requirements.  Also on the BGA density (of connnections).
Microvias range in size from 2-8 mils diameter.  Plating is typically
electroplated copper (although the photovia process is being demonstrated by
conductive inks provided by ORMET).  Most don't require microvias below 4-5
mils (because of the cost of manufacturing).

There is much more detail to go into, but your question is vague.  Do you
need to locate a laser drill shop, board supplier, etc?  Or is this
educational?

Shannah Tovah


-----Original Message-----
From: edward Edward Szpruch <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Date: Tuesday, September 14, 1999 5:06 AM
Subject: [TN] BGA micro-blind vias


>Hi,
>What is the common practice concerning blind-microvias located on BGA pads:
>a) open ? ( 2-3 mills diameter, 2 mills deep)
>b) filled with what ( fill materials,LPI solder mask)?
>c) filled with electroplated copper ?
>Pls advice
>
>Edward Szpruch
>Eltek , Manager of Process Engineering
>P.O.Box 159 ; 49101 Petah Tikva Israel
>Tel  ++972 3 9395050 , Fax  ++972 3 9309581
>e-mail   [log in to unmask]
>
>##############################################################
>TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
>##############################################################
>To subscribe/unsubscribe, send a message to [log in to unmask] with following
text in
>the body:
>To subscribe:   SUBSCRIBE TECHNET <your full name>
>To unsubscribe:   SIGNOFF TECHNET
>##############################################################
>Please visit IPC web site (http://www.ipc.org/html/forum.htm) for
additional
>information.
>If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
>847-509-9700 ext.5365
>##############################################################
>

##############################################################
TechNet Mail List provided as a free service by IPC using LISTSERV 1.8c
##############################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in
the body:
To subscribe:   SUBSCRIBE TECHNET <your full name>
To unsubscribe:   SIGNOFF TECHNET
##############################################################
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################